Although about 4% of light is reflected from one surface of a common glass, a severe obstacle may be caused during use of an optical component which requires high light transmittance. Therefore, an anti-reflective coating which reduces the loss of reflected light has been widely applied to both surfaces of a conventionally produced rear-view camera lens. The anti-reflective coating may be applied by vacuum deposition, but its manufacturing apparatus may be complicated and manufacturing cost thereof may be high.
Particularly, for the conventionally produced rear-view camera lens, the surface has been coated with an anti-reflective coating to improve transmittance by reducing light reflection. For example, as illustrated in FIG. 1, when the anti-reflective coating is performed on both surfaces of the lens, scattered reflection of light which is entered into the lens may be reduced and transmittance thereof may increase. The anti-reflective coating typically has a structure in which aluminum oxide (Al2O3) and magnesium fluoride (MgF2) are deposited as an anti-reflective material, and the entire thickness of the coating layer is about 120 nm. FIG. 1 shows a cross-sectional view of a conventional lens on which an anti-reflective coating is applied.
The conventional anti-reflective coating techniques may simply improve transmittance through the reduction of reflection, and when a functional coating layer such as a water-repellent coating, a hydrophilic coating and an anti-fogging coating is applied thereto additionally, adhesion between the anti-reflective coating layer and the anti-fouling coating layer may be very weak, which may result in deteriorating adhesive strength, and the coating process may not be efficient.
In such conventional anti-reflective techniques, Al2O3 is coated on the inside while MgF2 is coated on the outside. When a water-repellent coating is applied, weak durability and weather resistance may deteriorate due to repelling force between the fluorine functional groups located at the outside of the anti-reflective coating layer and the fluorine functional groups of the water-repellent coating. In the case of other functional coatings, binding strength may be reduced due to the fluorine functional group of the low reflective coating layer. Accordingly, it is difficult to apply such a functional coating to the anti-reflective coating.
In the related art, a method for manufacturing a lens having a functional nano-pattern has been developed. The method includes forming a photonic crystal pattern on a molded member and pressurizing the molded member on a curved unit of the lens, thereby forming the photonic crystal pattern on the surface of the lens. The above method may be useful for manufacturing a lens having a functional nano-pattern which improves light transmittance by minimizing the loss of reflection. However, the manufacturing process of the lens having such a pattern may be complicated. Furthermore, when the lens is used as a rear-view camera lens for vehicles, its transmittance may be significantly reduced due to light reflection.
Thus, in order to overcome above problems of the anti-reflective coated lens in the related art, a lens with improved coating properties, such as high transmittance by reducing of light reflection, super-water repellency, weather resistance and maximized durability, is strongly desired.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.